Conventionally, a speaker apparatus is known as an apparatus for converting a sound signal composed of music data of musical sound and voice into air vibration (sound electromechanical transducer). The speaker apparatus used widely in general is formed by: a speaker unit having a cone-shaped diaphragm for converting the sound signal into air vibration; and an enclosure (housing). Various efforts have been conventionally made to make the sound emitted from the speaker apparatus close to the original sound.
As an example, it is known that a speaker apparatus formed by directly arranging a speaker unit on a musical instrument for reproducing rich sound inherent in the musical instrument. For example, Patent Document 1 and Patent Document 2 disclose a speaker apparatus where a speaker unit is attached to a sound box or a sound hole of an acoustic guitar as a vibration generation source to use the sound box as an enclosure.